Enhanced removal rate of ARGs by inoculating microbial agents during the composting cooling period

Inoculating different microbial agents results in varying levels of antibiotic resistance genes (ARGs) removal, and there remains potential to further enhance removal efficiency. Moreover, the mechanisms driving ARGs removal under different inoculation strategies remain unclear. To improve ARGs removal efficiency, different microbial agents (single Bacillus subtilis and compound microbial agents) and inoculation timings (initial and cooling periods) were investigated, based on the correlations between microbial communities and ARGs. Results indicated that inoculation during the cooling period increased the overall ARGs removal rate to 93.99 %-97.07 %, with Bacillus subtilis achieving the highest removal rate of 97.07 %, exceeding that of inoculation during the initial period (84.19 %-88.8 %). This enhanced removal efficiency was primarily attributed to increased microbial community diversity, the enrichment of certain carbon- and nitrogen-decomposing bacteria, and a more effective reduction in ARG-hosting bacteria, which collectively contributed to improved ARGs removal. This study elucidates the mechanisms by which microbial inoculation at different composting periods enhances ARGs removal, providing guidance for improving ARGs mitigation in compost production.